This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Idiopathic pulmonary fibrosis (IPF) is a diffuse parenchymal lung disease (DPLD) of unknown etiology. Despite several decades of investigation, no treatment has been shown to stabilize or improve the disease. The diagnosis of IPF is difficult. High-resolution CT scans of the chest miss over 10% of biopsy proven and physiologically significant IPF [4]. Physiologically the group of DPLD are characterized by decreased compliance ([unreadable]V/[unreadable]P) and reduced lung volumes. MRI techniques appear to be uniquely suited to demonstrate the physiological and structural changes in the DPLD. The measurements are non-invasive, highly reproducible, and most importantly give regional information. Hyperpolarized gas MRI techniques have recently been developed to identify regional alveolar size, lung compliance, and alveolar oxygen levels, important parameters in DPLD. However, these techniques have not been routinely applied to small animals. We aim to demonstrate that three novel hyperpolarized gas metrics, lung compliance, regional alveolar size and alveolar oxygen levels, are uniquely suited to measuring lung alterations associated with pulmonary fibrosis. These measurements can potentially lead to better means of diagnosis of pulmonary fibrosis and to monitor responses to treatment.